1. Field of the Invention
The present invention relates generally to valves of the type which may be used to regulate the flow of fluids therethrough and more specifically, to an integral bleed system for such valves for permitting the selective release of pressure.
2. Prior Art
The design of many valves in the prior art permits pressure trapped in the body cavity to be relieved by means of pressure relieving devices. Such devices are designed to permit hydraulic communication of the fluid trapped in the body cavity to the upstream, downstream or external area of the valve body. At first glance this appears to be a relatively simple task, but upon further analysis it will be seen that this task is indeed quite overwhelmingly complex. As a result, prior art solutions have also been complex as well as clumsy and potentially dangerous. The complexity of the use of external pressure relieving devices stems primarily from the large array of variations that must be provided in a conventional bleed system and the number of parameters which can affect the nature of the bleed system in prior art valves. For example, the material of which the bleed systems are made will usually depend upon the nature of the media. Thus for example there may be two basic materials depending upon whether the media is caustic or not caustic. Material properties of external valve bleed systems will also vary as a result of differences in the temperature of the media and the viscosity of the media. There will also be variations in the geometry of end connections such as whether such connections are threaded or compression fittings, or pipe threads or unions and the like. Another significant variable is size. Variations in the bleed system configuration will depend upon the size of the pipes and tubes and the pipe schedules and the thicknesses of the tubes and the pipes. Other variations stem from variations in the manufacturer's specifications for valves. The sealing material will also result in variations necessary in the pressure relieving devices of the bleed system. Different relief valve requirements are also parameters which affect the complexity of such bleed systems. Check valve crack pressures also affect variations and manual valve styles with and without locking devices add additional parametric permutations. These variations quickly add up. Just those mentioned above represent over one million possible permutations. As a result, a large part of inventory control, purchasing, designing, and design control for valve manufacturers can be directly attributed to the relatively secondary issue of the bleed system.
Prior art pressure-relieving bleed systems are clumsy because once they are installed they require numerous joints which can leak. In addition, the bleed system normally protrudes from the valve body and as a result, handling and shipping becomes more difficult. Once installed, the bleed system with its required maintenance access area, virtually doubles the original valve installation dimensional requirements. The dangers of an external pressure relieving bleed system of the prior art stem from the fact that once the valve is installed, the relatively weak structure of the bleed system is attached to an immobilized valve and provides protruding plumbing and valves such as relief valves and the like. Such protrusions can easily be broken off creating significant dangers. A bleed system that becomes severed can create the possibility of a catastrophic failure including fire, explosion, hazardous material spills and the like.
There is therefore a significant need for an improved valve pressure-relieving bleed system which overcomes the aforementioned disadvantages of prior art bleed systems. In other words, there is a need for a bleed system that does not require a significant inventory to accommodate large variations in the parameters of such bleed systems; which does not produce a clumsy and dangerous external plumbing configuration and which reduces the possibilities of a catastrophic failure of the type described above.